Good news, everyone. Today, in addition to releasing OS X 10.10.3 and iOS 8.3, Apple released Security Update 2015-004 for 10.9 and 10.8. This update appears to fix the EPPC bug introduced in Security Update 2015-002. The bug prevented access to Remote Apple Events over the EPPC protocal. Anyway, I had no problems with a couple of simple tests.
Fast turnaround, actually.